This application is based on Japanese Patent Application No. 2002-49948 filed on Feb. 26, 2002 the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an engine control apparatus for executing a cylinder determining processing of a multi-cylinder engine by using a crank sensor and a cam sensor.
2. Description of Related Art
As this type of conventional technology, a cylinder determining and detecting apparatus for an internal combustion engine disclosed in JP-A-5-133268 is known in the art. According to the apparatus disclosed in the document, it discloses a method for detecting rotation of a crankshaft and a camshaft of a four-cycle engine by a crank sensor and a cam sensor respectively, and for executing a cylinder determining processing on the basis of the detecting results of the sensors.
More specifically, the crank sensor has a rotor the outside of which is provided with protrusions in even intervals and with an absence tooth portion which is formed by removing a part of the protrusions. The cam sensor has a rotor the outside of is provided with protrusions in even intervals and with an auxiliary tooth in one location. The absence tooth portion and the auxiliary tooth correspond to a predetermined angular position, e.g., top dead center, of a predetermined particular cylinder. Therefore, it is possible to determine the cylinder based on the crank sensor alone. It is also possible to determine the cylinder based on the cam sensor alone. In addition, it is also proposed that a method for executing a cylinder determining processing on the basis of a combination of the detected signals of both sensors.
According to the apparatus in the above document, even if one of the crank sensor and the cam sensor fails, it is still capable to execute the cylinder determining processing in a successful manner using the other one of the sensor signals.
However, a detection of the absence tooth of the crank sensor is executed every rotation of the crankshaft, that is every 360xc2x0 CA. In case of the multi-cylinder four-cycle engine, the absence tooth is detected at predetermined angular position, e.g., top dead center, of two cylinders. Therefore, in case of that the cylinder determining processing is temporarily suspended due to abnormalities of both the crank sensor and the cam sensor while the engine is operated, even if only the crank sensor is recovered to normal, it is impossible to determine the particular one of the cylinders based on the cylinder determining processing using the crank sensor alone.
In that case, if an engine speed is low such as during the starting of the engine, a serious problem would not arise, since even if an incorrect cylinder is determined, it merely causes an engine stall or the like. However, if an incorrect cylinder is determined under a normal operating condition, e.g., under a high-speed rotation, several problems may arise, since the engine will rotate continuously due to an inertia of itself. For example, by injecting fuel to the incorrectly determined cylinder, it may cause problems such as emissions of unburned fuel and damages of the engine.
The present invention was accomplished in consideration of the above-mentioned circumstances. It is therefore an object of the present invention to provide an engine control apparatus that is capable of executing the cylinder determining processing in an appropriate manner, and resolving the above-mentioned problems due to an incorrect cylinder determination.
According to a first aspect of the present invention, a crank sensor detects rotation of a crankshaft, and outputs a crank signal including angle indicating parts and reference position indicating parts. In addition, a cam sensor detects rotation of a camshaft, and outputs a cam signal including angle indicating parts and reference position indicating parts. The apparatus is provided with a first cylinder determining means and a second cylinder determining means as means for determining cylinder. The cylinder determination is carried out on the basis of the crank signal, and the cylinder determining processing is carried out on the basis of the cam signal too. A sensor signal abnormality detecting means detects an abnormality of the crank signal and the cam signal respectively. A cylinder determination controlling means prohibits the cylinder determining processing of the first cylinder determining means when both the crank signal and the cam signal become abnormal while operating the engine. Then, the cylinder determination controlling means withdraws the prohibition of the cylinder determining processing on the condition that the cam signal is recovered normal.
In the case when a previously executed cylinder determining processing is suspended due to the abnormalities of both the crank signal and the cam signal, the cylinder determining processing may be resumed if the cam signal is recovered to normal. In this case, even if the crank signal is recovered earlier, the cylinder determining processing using the crank signal alone is still prohibited. If the crank signal is still abnormal when the cam signal is recovered, the cylinder determining processing is executed by using the cam signal alone. There is a possibility to make an incorrect cylinder determination on the basis of the crank signal alone. However, the incorrect cylinder determination can be prevented since the cam signal enables a determination of one particular cylinder by using itself alone. As a result, by executing the cylinder determining processing of the engine in an appropriate manner, it is possible to resolve several problems due to the incorrect cylinder determination.
The cylinder determining processing may be prohibited on the condition that an engine speed is higher than a predetermined speed in addition to the condition that both the crank signal and the cam signal are abnormal.
A result of the cylinder determining processing may be inverted oppositely when it is not detected to increase an engine speed by monitoring change of the engine speed after a completion of the cylinder determining processing of the first cylinder determining means when starting the engine. In the starting of the engine, even if the cylinder is incorrectly determined, it merely makes it difficult to start the engine, and the engine is not damaged. It is possible to determine the cylinder correctly by just inverting the result of the cylinder determination in a relationship of a front side and a backside. Here, in case of the four-cycle engine, two cylinders distanced by 360xc2x0 CA are considered as the cylinders in the front side and the backside.
The prohibition of the cylinder determining processing caused by the cylinder determination controlling means may be withdrawn when the engine stalls. In this case, since a restarting operation might be carried out if an engine stall occurs, it is possible to execute the cylinder determining processing using the crank signal alone even if the cam signal is continuously abnormal.
The cylinder determining processing may be executed by referring to reference position detecting data of the cam signal in response to the detection of the reference position of the crank signal. In this case, the results of the cylinder determining processing are stored as a history at every time of the cylinder determining processing. Then, the result of the cylinder determining processing is examined to determine whether or not it is correct on the basis of the history characterized by a plurality of results of succeeded cylinder determining processing. In case of executing the cylinder determining processing on the basis of a combination of the crank signal and the cam signal, there is a possibility to make an incorrect cylinder determination if a pulse is incorrectly recognized due to a noise or the like. On the contrary, according to the invention, it is possible to achieve an anti-noise measure.
The prohibition of the cylinder determining processing may be withdrawn on the condition that an engine speed is decreased to a predetermined speed after both the crank signal and the cam signal became abnormal. Although the crankshaft and the camshaft are mechanically coupled and rotate in keeping an angular synchronousness, an angular position between them might be shifted in a high-speed rotation. For example, in case of coupling the crankshaft and the camshaft by a chain, a phase difference may appear between the crank signal and the cam signal at the high-speed rotation. Taking such circumstances into consideration, it is preferable to withdraw the prohibition of the cylinder determining processing only when the engine is operated in a low-speed range, less than a predetermined speed. Thereby, a reliability of the cylinder determining processing is improved.